In the realm of optical device packaging, there is beginning to develop a number of assemblies which utilize a single crystal semiconductor material (such as silicon) as the support structure for the various optical devices. Often referred to as “silicon optical bench” technology, the utilization of silicon may result in a significant cost saving in optical packaging over some of the more esoteric materials that have been used in the past. More importantly, silicon processing technology has advanced to the stage where a number of relatively simple procedures (e.g., oxidation, isotropic etching, anisotropic etching, etc.) may be utilized to facilitate attachment of the devices to the support member, as well as alignment therebetween. Further, it is possible to form optical waveguiding structures directly in/on a silicon substrate, resulting in the ability to form a completely operable optical subassembly in silicon.
An exemplary utilization of silicon in the formation of a subassembly for optoelectronic devices is disclosed in U.S. Pat. No. 4,945,400, issued to G. E. Blonder et al. on Jul. 31, 1990. In general, Blonder et al. disclose a subassembly including a semiconductor (e.g., silicon) base and lid including a variety of etched features (e.g., grooves, cavities, alignment detents) and metallization patterns (e.g., contacts, reflectors) which enable an optoelectronic device to be reliably and inexpensively mounted on the base and coupled to a communicating optical fiber. In particular, Blonder et al. disclose an arrangement wherein the optoelectronic device (e.g., LED) is disposed within a cavity formed by a lid member and the communicating fiber is positioned along a groove formed in a base member. A reflective metallization is utilized to optically couple the device to the fiber. Therefore, positioning of the active device with respect to the reflective metallization is the only active alignment step required to provide coupling.
An advance in the area of silicon optical bench packaging is disclosed in U.S. Pat. No. 5,179,609 issued to G. E. Blonder et al. on Jan. 12, 1993. In this arrangement, separate silicon piece parts are used to support an active optical device and a communicating optical fiber. A bare fiber is supported in an etched V-groove formed in a first silicon piece part and fiducials are formed in both piece parts to provide mechanical registration and alignment between the optical fiber and the active device when the two piece parts are mated.
Although such an arrangement is useful in a number of applications, the capability of providing passive alignment with micron-level tolerances becomes problematic, and the need to utilize a number of mating components (e.g., alignment detents and spheres, for example), becomes time-consuming and expensive for high volume production applications.
Thus, a need remains in the art for a simple and efficient technique for providing improved alignment between an optical fiber and active optical device.